Parshiot Nitzavim-Vayelech: Going When It’s Time

Moshe’s goodbye speech that is the book of Devarim contains a number of references to the fact that he will not accompany the people into the Promised Land. He talks about how he requested, knelt, pleaded before G-d to be given a chance to enter the land — if only for a short time — and how each request was summarily rejected.
In the beginning of Devarim, Moshe pins the reason on the event of the spies (1:37). Sometimes, the reasoning becomes more of G-d’s design than a mundane punishment. The Or HaChaim (1:37) quotes a gemara (Sotah 9a) and the Midrash Tehillim (79) to explain how Moshe’s non-entry into the land was part of a plan that would ultimately save the Jewish people. Had Moshe entered the land, he would have built the Temple, which G-d would never allow to be destroyed.
G-d’s ensuing wrath over the people turning from Him was taken out on wood and stones (the destruction of the Temple), rather than against the Israelite nation.
In his work Siftei Tzadikim, Rabbi Menachem Mendel of Rimanov says that Moshe, the ultimate shepherd of Israel, fulfilled his destiny particularly in death, through granting Israel an everlasting chance at eternal survival.
To bring the matter to an even more direct level, the Mareh Yechezkel (Rabbi Yechezkel Panet) gives two additional explanations for why Moshe needed to remain outside of the land: for the merit of those who perished in the wilderness, and to serve as a defense against the prosecution of Baal Peor, who would not be able to stand up against Moshe’s grave, which is in the mountains of Moav, overlooking the place where the negative incident of Bamidbar 25 took place.
In our parsha, Moshe says “Today I am 120 years old and I can no longer come and go. G-d has [also] told me that I would not cross the Jordan.” (31:2)
What does Moshe mean when he says “I can no longer come and go?” Is Moshe referring to his physical prowess? Is Moshe referring to the reality that the end of his life has arrived? Is Moshe saying that he can no longer argue the point with G-d because it is hopeless for him to enter the land?